Venetian Conspiracy

The Venetian Conspiracy was a plot by the House of Barbarigo and the Knights Templar to convince Doge Giovanni Mocenigo to bow to their influence or murder him. They eventually murdered him after Carlo Grimaldi's efforts to enlist Mocenigo's aid failed, and Marco Barbarigo became the new Doge, but they were hunted down by Ezio Auditore da Firenze and all of the conspirators were killed.

Background
The House of Barbarigo were the most influential family in the Republic of Venice during the mid-15th century, taking over the silk and spice trade and all of the commercial interests in the city. Emilio Barbarigo almost single-handedly funded the Venetian police force, and in turn had himself and his family exempted from taxes, and they also eradicated all crime and opposition. By 1481 the family had been enlisted as Templar agents, as they wanted control of Venice, which would also make Venezia fall under Templar influence. The plan had a mutual benefit for both sides, so they agreed to ally.

War
The Assassin Ezio Auditore da Firenze overheard Jacopo de Pazzi talking of a Templar presence in Venezia while eavesdropping on him in 1480, which is why he traveled from Florence to Romagna and then to Venice. Ezio assisted the Thieves' Guild of the city in bringing down Emilio Barbarigo, killing him in his own palazzo.

Doge Giovanni Mocenigo was the center of the plan: he needed to be convinced to accept Templar sovereignty over Venice or be killed by the Barbarigos. Despite Council of Ten member Carlo Grimaldi's efforts, Mocenigo would not listen to the sycophant and instead remained independent. Grimaldi bought time, and time and time again attempted to convince him. When it failed, Marco Barbarigo told him that they must kill the Doge. Silvio Barbarigo supplied arsenic poison for Grimaldi to put onto the Doge's meal, which would be hard to trace.

Ezio and Antonio de Magianis spotted a way to enter the Palazzo Ducale, through the Basilica of San Marco, and he overheard Carlo Grimaldi threatening the Doge. When Antonio remarked that only birds could enter the palazzo, Ezio remembered Leonardo's flying machine that he invented. He decided to test Leonardo's machine by jumping off a tower, attempting to control his weight in order to determine weight and direction. He eventually crashed, but Leonardo was happy that he flew. He tried to find a way how to extend the flight distance, and by seeing paper in a fire, he remembered that heat rises, and it could lift the wings of the machine.

Ezio and Antonio made a new plan: Ezio would take care of the guards so Antonio and his men could light the fires needed to provide lift for the flying machine. He assassinated all of the guards, and returned to Leonardo and Antonio, who readied him for the mission.

Flying over many bonfires, Ezio used the machine to get to the roof of the Palazzo Ducale, before letting it crash into the dockyards. Ezio attempted to warn the Doge that he had been poisoned, but Grimaldi told him that he was already dead, and the Doge choked soon after. Ezio chased Grimaldi, who said that he had killed the Doge, and he stabbed him in the back of the head with hidden blades. Shortly after, the Doge came onto the staircase and fell down, dying of the poison.

Due to the Doge's death, Marco Barbarigo became the next Doge, according to plan. He was paranoid and rarely left the Palazzo Ducale, but during the Carnivale, he held the largest festival of all. Pickpocketing Dante Moro of a special mask that let him into the party, Ezio entered the carnival and used his hidden pistol to shoot Marco through the heart aboard his boat.

End of the War
After Marco's death, his pro-Assassins brother Agostino Barbarigo became the new Doge and he helped Ezio formulate a plan to take on Silvio and Dante, who were barricaded in the armory with 200 mercenaries. Ezio sought the help of condotierro Bartolomeo d'Alviano, freeing him and his men and positioning them in many places around the city. Most of the mercenaries left the armory, a perfect chance for Ezio to strike. He killed both of them with his hidden blades at the same time, and found out that the boats in the harbor were meant to go to Cyprus.

Aftermath
The last of the Venetian conspirators were killed, and Rodrigo Borgia failed in his plot to take over control of Venice. He was also forced to give up a Piece of Eden shortly after, and he retreated in anguish. Two of his conspiracies had failed, but he did not give up.